In the past, the motion picture industry has employed sound track recording on a 0.1 inch wide strip of the 35 mm film carrying visual images. Sound is usually recorded on film by means of varying the exposure to light corresponding to sound vibrations. Synchronization of sound with pictures allows video images to be accompanied by analog data regarding the images. Foreign language films are usually provided with subtitles on the visual image to accompany the sound.
Weinstein teaches in U.S. Pat. No. 3,932,032 a system for digitally recording sound on motion picture film. In one embodiment a laser scanner enters a digital representation of the sound on the same frame as the corresponding picture. A projector capable of using this film employs a strip of photodetectors to recover the sound. LeVine in U.S. Pat. No. 4,461,552 uses pulse code modulation to sample sound. Digital codes are optically applied to the film sound track and optically detected when the film is played back through a projector. A modulated laser is used with a controllable refraction optical crystal or Bragg cell to scan the sound track for recording and reading. One problem is that the sound data must be developed along with the film. Until the film is developed there is no way to hear what was just recorded.
In the field of archival data storage, it is frequently necessary to store audio-visual information. Adding digital information by means of a small laser recorder could be of considerable value for stored motion picture film. Such add-on records have a potential of getting separated from the recorded film during storage in archives. Even if not separated, the differences in archival storage properties, say between film and paper, pose storage problems.
An object of the invention is to provide a method for digital recording of sound or of editing information along with motion picture film.
A further object of the invention is to provide this method where the sound may be immediately played back for review.
A further object of the invention is to provide control signals synchronized with the film which can be used to control other audiovisual devices in synchronism with the film.